1. Field of the Invention
The invention relates to a vacuum system, comprising an evacuatable housing, an object holder and an object carrier which is detachably coupled thereto. The object holder comprises positioning means which are situated partly within the housing and which serves to position an object in the housing. The object carrier comprises a supporting element having a supporting surface for the object and which is rotatable about an axis of rotation with respect to the object carrier. The carrier includes drive means which cooperates with the supporting element and the positioning means.
The invention also relates to an object carrier suitable for use in a vacuum system.
2. Description of the Prior Art
A vacuum system, notably an electron microscope, and an object carrier of the kind set forth are known from German Patent Specification DE which corresponds to U.S. Pat. No. 4,292,523.
The cited Patent Specification describes a vacuum system including an electron-optical column which comprises an object holder in the form of a table which is slidable with respect to an optical axis of the column. An object carrier in the form of an object cartridge is introduced into the vacuum system and is coupled to the table. The object carrier has a tubular shape and contains an object to be examined which is suspended from a supporting element. The supporting element is pivotable about an axis of rotation with respect to the object carrier, which axis of rotation extends transversely of the optical axis and parallel to a supporting surface engaging the object. The supporting element is connected to a spring at one side and to a push member on another side, which push member engages a cam ring connected to the column. A position of the object can be adjusted with respect to the optical axis by rotation of the cam ring by means of positioning means which comprise a flexible shaft which emerges from the column. An object carrier and object holder combination of this kind is mechanically stable, but occupies a comparatively large volume in the direction of the optical axis. As result, the number of feasible lens configurations are limited because the volume occupied by the object carrier precludes the presence of pole shoes of a magnetic lens. Furthermore, the known object carrier does not permit concentric object motions where the point of intersection of the axes of rotation is situated on the optical axis.
It is to be noted that an object holder of the kind set forth is known per se from: C. J. Rakels, J. C. Tiemeijer and H. W. Witteveen, "The Philips Electron Microscope EM 300", Philips Technical Review, Vol. 29, 1968, No. 12, pp. 370-386.
The cited article describes an object holder in an electron microscope in which the cylindrical member can be mvoed out of the vacuum space in order to provide a tip of the cylindrical member with an object. In that case the tip constitutes the object carrier. A rotation of an object about an axis of rotation extending parallel to the optical axis is achieved by rotation of the spherical bearing and is limited as regards angle of rotation.
In a known object holder, a cylindrical member is arranged so as to be detachable from a spherical bearing in order to enable an exchange of objects, so that permanent vacuum sealing is not possible and, for example, an O-ring must be used for sealing.